I believe your idea is to use the LPG gas sensor MQ5 to detect the leak of gas and a GSM module to send a message or call alert in the event of a fire.

So basically you need a fire sensor, a Gas sensor and a GSM module interfaced to the Arduino Board. Since you idea is unique I doubt you will get any direct circuit diagram for your project. But, Instead you can combine 3 tutorials to build your project. The link for all the three projects are given below

Yes as Violet said, its not difficult to add MQ5 gas sensor and GSM module with Arduino. You can use the same connections for Arduino and GSM module given in the below schematic, and then add the gas sensor's output pin to one of the analog pin of Arduino.

In the above given links, you will also find the code for both getting the input from gas sensor and sending a message using GSM module. You just need to combine both the codes properly according to the arduino connections.